It is well known to measure electromyographic (EMG) signals from different parts of a human body during sports performances, the most common example being hear beat measurement using a surface EMG sensor-containing heart beat belt with a wireless transmitter module for communicating with a monitoring device, such as a sports watch. Measurement of surface EMG signals also from other parts of the body to monitor muscle activity in legs, arms, middle body or torso, for example. Such measurements can be carried using EMG sensors for example integrated into sports garment. It is also known to integrate signal transmitter modules into the belt or garment or to provide the module as a snap-on module to an assembly zone on the garment or belt. The module can be removed for washing the garment, for example. One disadvantage in known systems is that, although the transmitter can be removable and reconnectable, each sensor or sensor group requires a specifically designed transmitter module in order to operate properly.
To mention some specific examples, U.S. Pat. No. 8,253,586 discloses a performance measuring system comprising an article of clothing with an integrated measuring sensor and additionally a communication module, power module and computing module attachable to the article of clothing. The modules can be removed from one article of clothing and used in another article of clothing, while the sensor remains in the article. EP 1531726 discloses the use of a multitude of surface EMG electrodes to gain information simultaneously from muscles in various parts of the body. Also U.S. Pat. No. 4,583,547 relates to a similar application and in particular how conductive paths in garment can be arranged to provide a sensor signal form the measurement point to the signal transmitter module.
US 2008/0319330 discloses as a further example of currently available techniques a mobile transmitter for observing performance-related events and transmitting data on the observed events to a receiver. The transmitter comprises a timer for providing time references relating to the events and a memory for recording time references. The transmitter obtains a time reference from the timer and records the obtained time reference in the memory and is adapted to produce data messages containing a predetermined number of time references obtained from the memory and further to transmit the produced data messages to the receiver. The disclosed system allows for time stamping of events, such as heartbeats, and calculating the frequency and/or interval variation parameters of heartbeats. The system does not allow for synchronizing events from different detector sources.
U.S. Pat. No. 7,698,101 discloses a system for pairing sensor-containing shoes with measurement electronics, including authentication of the shoes for the electronics. Also these solutions require dedicated transmitter module sensor pairs in order to be able to transmit the measurement signal to a monitoring unit. US 2013/0096704 discusses articles of clothing and module capable of sensing physical and/or physiological characteristics associated with the use of the clothing. The module contains one or more integral sensors. The system can activate the module or sensor in it upon engaging the module to the clothing and confirm that the clothing and the module are authorized for use with one another and/or for automatic data processing algorithm selection. The flexibility of the system is, however, restricted to adaptation of the sensor module to use its built-in sensor in different ways depending on the clothing it is attached to. Thus, several modules are still needed or a single module needs to be equipped with a plurality of sensors if different types of signals are to be measured.
One problem also touched by the abovementioned publications in a multi-sensor system is the communication of the different EMG measurement signals to a single monitoring device. There are systems, which utilize wired communication channels from a plurality of sensors to a single module. Such systems become impractical if there is a need to use many sensors at distant body parts and potentially separate belt or garment units.
An additional problem in existing systems is how to handle signals from a plurality of sensor sources such that an overall analysis of the performance would be possible. In particular in wireless communication systems, a monitoring unit can relatively easily collect data from several sources, but may still lack information on the relationship of the data to each other and/or the performance.
Thus, there exists a need for improved solutions for facilitating communication between a plurality of sensors and a central monitoring unit to allow for better analysis of the performance.